Supplementary material from: Fiddler crab claws work as a deflection antipredator defence

Fiddler crabs exhibit conspicuous claws used for social signaling, which may also function as a deflection mechanism by diverting predator attacks from vital body regions. To test this hypothesis, we used robotic models replicating the colors and waving display of Gelasimus vomeris, deploying them in the field to be attacked by Australian brush-turkeys (Alectura lathami). We analyzed whether attack direction varied with claw conspicuity. Our results show that models with conspicuous claws attracted significantly more attacks to the claw, while those with non-conspicuous claws were primarily attacked on the carapace. This suggests that claw coloration reduces predation risk by deflecting attacks away from vital areas. The dataset includes spectral reflectance measurements of models, 3D files for claw replication, and videos documenting both experimental and natural waving behaviors. This study provides the first evidence of a claw-deflection strategy in crustaceans.